(a) Technical Field
The present disclosure relates to a display device with sensing units and a driving method thereof.
(b) Discussion of the Related Art
The weight and thickness of display devices need to decrease along with the ever decreasing weight and thickness of personal computers and televisions. Accordingly, cathode ray tubes (CRTs) may be replaced with flat panel display devices.
Flat panel display devices may include, for example, a liquid crystal display (LCD), a field emission display (FED) device, an organic light emitting display (OLED), and a plasma display device (PDP).
Each of the active flat panel displays may include a plurality of pixels arranged in a matrix, where the intensity of light is controlled based on luminance information of each of the pixels to display images. LCDs among the active flat panel displays may include a pair of panels that are provided with pixel electrodes and a common electrode, and a liquid crystal layer with dielectric anisotropy interposed between the two panels.
The LCD generates an electric field by applying voltages to the pixel electrodes and the common electrode. The magnitude of the electric field may be varied to adjust the transmittance of light passing through the liquid crystal layer, thereby displaying images.
A touch screen panel may be used to draw characters or pictures on a screen through contact with a finger, a pen, etc. Touch screen panels may also be used to perform a desired command by executing a program when a particular icon is pressed. An LCD with an attached touch screen panel determines whether a contact has occurred and the position of the contact.
However, adding a touch screen to an LCD may increase the cost of a display, decrease the yield due to the addition of a manufacturing process for bonding a touch screen panel on a liquid crystal panel, deteriorate luminance of the liquid crystal panel due to the passage of light through an additional layer, or increase product thickness.
Technology has been developed that provides sensing units within pixels that display an image in an LCD. As a result, an additional touch screen panel is not required. The sensing unit senses a variation of light or pressure applied to a screen of the LCD by a finger, pen, etc. of a user, to determine whether there has been contact with the screen and the position of the contact.
The sensing units include a plurality of row sensing units for sensing row coordinates (Y-axis coordinates) and a plurality of column sensing units for sensing column coordinates (X-axis coordinates). The row sensing units are connected to column signal lines extending in a column direction, and the column sensing units are connected to row signal lines extending in a row direction.
However, since the row and column signal lines extend in different directions, the row and column signal lines are formed in different layers from each other. The response speed of the row and column sensing units at a contact position may be different due to a height difference of the row and column signal lines, thereby decreasing the reliability of the LCD's ability to sense a touch. Thus, there is a need for an LCD which is more reliable at sensing touches.